<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>一元运算符</title>
</head>
<body>
<script>
    var o = new Object({
        toString() {
            return '返回的值';
        }
    });
    o.userName = '雨夜';
    console.log(o.userName);
    delete o.userName;
    console.log(o.userName);
    console.log(o.toString());
</script>
</body>
</html>